1. Field of the Invention
This invention relates to a sheet stapling apparatus including a noise reducing work clamp.
2. Background of the Invention
Electrostatographic copiers and printers for example are well known. As is known, each such a copier or printer can produce a series of pre-collated copy sheets which can then be complied by an attached finisher portion of such printer or copier into a stacked set of sheets for binding together. As disclosed in commonly assigned U.S. Pat. No. 4,318,555 issued Mar. 9, 1982 in the name of Adamski et al, the use of a stapling system or apparatus to effect such binding is well known. Typically, such stapling apparatus comprises a stapler head including means for holding and driving formed staples into a set of sheets, and a clincher head for clinching the leg portions of a staple so driven through the set of sheets. It is also typical for the clincher head to consist of a pair of solid, stationary or slightly movable die-face members, and of means for moving such members. As such, the clincher head, as a whole, has few parts and is relatively rugged and reliable. Where the stapling apparatus uses continuous staple material such as wire to form such staples, a wire feeding mechanism for feeding wire to the stapler head thereof is also included. The wire feeding mechanism is thus associated with the stapler head which includes means for shearing a desired length of wire from the continuous wire, means for forming a staple from such cut length of wire and means for driving the formed staple through a set of sheets.
As is well known, in order for any such typical stapling apparatus to operate successfully in binding a set of sheets, the apparatus must also include means for clamping and holding the set of sheets together during the staple driving and leg clinching functions of the apparatus. Conventionally, such means for clamping the copy sheets is comprised of two members which consist of a stationary clincher head, and a movable stapler head. However, as also disclosed in related application Ser. No. 608,098 entitled STAPLING SYSTEM WORK CLAMP and filed herewith on even date, the work clamp may also consist of a stationary stapler head, and a movable clincher head.
In either case, the copy sheets or work pieces to be clamped are fed into registration over the stationary member, and the movable member is then moved with a desired force from a remote position into a contact position with the copy sheets in order to properly compress the sheets for efficient stapling. Ordinarily, the movable member is moved thus under the load or force applied by means such as a solenoid or a spring, or a combination thereof. The movable member therefore may travel at an accelerated speed or a constant speed, and will contact the sheets with a certain impact force.
Unfortunately, the number of sheets making up a set to be clamped and stapled can vary unpredictably from a minimum of two, to a maximum, for example, of 50 (fifty) sheets or more. Yet each such set must be tightly clamped in order for the stapling and clinching operations of the stapling system to be performed effectively. As such, the force and velocity with which the movable member contacts the sheets must be set initially so as to achieve a tight and effective clamping of the maximum number of sheets, for example 50 or more. During each such clamping operation, the number of sheets in the set actually behaves as a cushioning or dampening means between the stationary and movable members of the clamping means. When the force and velocity of the movable member is set for effective clamping of the maximum number of sheets, this unfortunately creates serious and undesirable noise and vibration problems when much smaller sets with as few as two sheets are clamped. This is because there is not enough cushioning and dampening of these latter cases as there is in the case of the maximum or near maximum number of sheets.